In a conventional tensioner for maintaining tension in a flexible, endless, traveling transmission medium, such as the timing chain in an internal combustion engine, a plunger protrudes from a housing and has a shoe at its outer end for sliding contact with the traveling transmission medium. The plunger is urged in the protruding direction by a biasing device, such as a coil spring, inside the tensioner housing. Stoppers have been used to maintain the plunger in a retracted condition, and to prevent the plunger from separating from the tensioner housing during shipping and during installation on an engine. An example of a conventional stopper is depicted in FIG. 6 of Japanese Laid-open Patent Publication No. Hei. 7-42805. Another example of a conventional stopper is described in U.S. Pat. No. 5,676,614, and shown in FIGS. 8 and 9, FIG. 8 being a front elevational view of a tensioner having a conventional stopper, and FIG. 9 being a cross-sectional view taken on plane 9-9 of FIG. 8. In these figures, a tensioner 51 includes a shoe 56, which comes into sliding contact with a chain 55, and a cylindrical plunger 54, which is caused to protrude from a housing 52 by a coil spring 58 in a direction to maintain tension in the chain. The plunger is slidable in a cylindrical bore 53 in the housing, which, together with the plunger 54, defines a hydraulic chamber 57. Oil is supplied under pressure to the chamber 57 from an oil passage (not shown) through a check valve 59.
A guide surface 60, formed On a side of the housing 52, extends in parallel relation to the protruding direction of the plunger 54. An extension 62, facing the guide surface 60, is formed as an integral part of shoe 56, and prevents rotation of plunger 54 about its axis. A pin-receiving hole 63 is formed in the guide surface 60, and a through hole 64 is formed in the extension 62. Hole 64 can be aligned with the pin-receiving hole when the plunger 54 is pushed into the cylindrical bore 53.
By aligning the holes 63 and 64, a pin 61a of a stopper 61 which comprises the pin 61a and a handle 61b, can be inserted through hole 64, and into hole 63, to secure the shoe 56 in fixed relation to the housing 52, and prevent the plunger from being pushed out of the housing by spring 58. After the tensioner is mounted, when the stopper 61 is pulled out, the plunger 54 can protrude and press the shoe 56 against the chain to impart tension to the chain.
Where a tensioner is used in the timing chain system of certain types of automobile engines for example a V-type, double overhead cam (V-DOHC) engine, it may be situated in a very restricted space. In the timing system shown in FIG. 10, for example, a first chain C1 is in mesh with a crankshaft sprocket S1 and two cam sprockets S2 on the camshafts that operate the air intake valves of the engine. Second air-intake cam sprockets S3 are coaxial with, and rotate with, sprockets S2, and chains C2 mesh with sprockets S3 on the air intake camshafts, and sprockets S4 on the exhaust camshafts, so that the exhaust camshafts are driven in synchronism with the air intake camshafts. Tensioner T1, situated along the path of chain C1 between sprocket S1 and one of sprockets S2, controls tension in chain C1 through a pivoting tensioner lever L1. Tensioners T2, each of which is situated between a sprocket S3 and a sprocket S4, control tension in chains C2. Fixed guides G1 and G2 are also provided along the path of chain C1.
When the tensioners T1 and T2 are mounted on an engine, they are typically mounted in spaces that are restricted by the presence of various engine structures and fittings, including fittings associated with the cam sprockets. In particular, the tensioners T2, which apply tension to chain C2, are mounted in very restricted spaces on the insides of the loop-shaped paths of chains C2, where various engine structures are gathered. However, because the stopper 61 in the conventional tensioner 51 is straight, that is, its handle 61b and its pin 61a are aligned along a common axis, the stopper can come into contact with the engine frame or its sprocket fittings, which makes the mounting of the tensioner difficult. Moreover, after the tensioner is installed and the various parts of the timing system are assembled, there is little available space to allow removal of the stopper. Accordingly, in some engine configurations, it is not possible to utilize a tensioner having a stopper of the kind depicted in FIGS. 8 and 9.